<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>


    <script>

        var age = +prompt('请输入您的年龄');
        // 声明变量
        alert(age);
        // 弹出
        console.log(age);
        // 打印
        var age1 = age + 5;
        // 声明age1
        var str = '据我估计，五年后，你可能' + age1 + '岁了';
        // 声明str
        alert(str);
        // 弹出str
    </script>
</body>

</html>